Java The Boolean Type

The Boolean type represents true / false values. Java defines the values true and false using the reserved words true and false. Thus, a variable or expression of type boolean will be one of these two values. Here is a program that demonstrates the boolean type:
// Demonstrate boolean values.
class BoolDemo
{
public static void main(String args[])
{
 boolean b;
b = false;
System.out.println("b is " + b);
b = true;
 System.out.println("b is " + b);

// a boolean value can control the if statement 

if(b) System.out.println("This is executed.");

b = false; 

if(b) System.out.println("This is not executed.");

// outcome of a relational operator is a boolean value System.out.println

("10 > 9 is " + (10 > 9));

}

}

The output generated by this program is shown here:

b is false 

b is true 

This is executed. 

10 > 9 is true

There are three interesting things to notice about this program. First, as you can see, when a boolean value is output by println( ), “true” or “false” is displayed. Second, the value of a boolean variable is sufficient, by itself, to control the if statement. There is no need to write an if statement like this:

if(b == true) ...

Third, 

the out come of a relational operator, such as <, is a boolean value. This is why the expression 10 > 9 displays the value “true.” Further, the extra set of parentheses around 10 > 9 is necessary because the+operator has a higher precedence than the>.